| dc.description.abstract | During the last few years, wireless networks have been rapidly growing and becoming more and more popular. In particular,telematics are receiving a lot of attentions due to wide variety ofservice which are safety, GPS navigation, multimedia, streaming, and other Internet applications. With the matured wireless transmission technology, the new demand on wireless applications is toward the concept of deploying wireless devices on transportation systems such
as buses, trains and vehicles. Telematics services and entertainment are also important for users.
Dedicated short range communications (DSRC) technique has been formally defined by American Society for Testing and Materials (ASTM) association couple years ago. Subsequently, the DSRC standardization process has been smoothly transferred to the IEEE 802.11p working group for the consideration of world-wide market and regulatory. Moreover, some documents released from IEEE 1609 Working
group (e.g., IEEE 1609.3 and IEEE 1609.4), which name the DSRC system as wireless access vehicular environment (WAVE), have defined that the wireless communication technique among vehicles and roadside system mainly inherits from IEEE 802.11a physical (PHY) layer and IEEE 802.11 carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol. Generally, number of antennas which each vehicle equips with is limited. If vehicles transmit and receive data over wireless medium, they shall contend each other on the same wireless channel. However, it usually suffers from packet collision, which decreases data throughput and increases delay as the number of vehicle increases. Moreover, the mandatory operation of channel switching between service channel and control channel will waste half channel resource. It is desired to have a smart channel access scheme for the vehicular networks.
In this dissertation, we propose coordinated channel access schemes including coordinated interleaving access (CIA), agent-based coordination (ABC), vehicular grouping access (VGA) under different roadway environments, and memorized carrier sense multiple access with collision avoidance (MCSMA/CA) so that the channel utilization is increased from 42\% to 100\% as compared to the alternating channel access scheme and system performance is improved significantly.
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